a) HCT116 WT and PTTG1−/− cells expressing an empty vector (WT+EV and PTTG1−/− +EV), and PTTG1 re-introduced PTTG1−/− (PTTG1−/− +PTTG1) cells were plated in 96-well plates and DNA synthesis assessed at different time points (time 0 represents 0 hours after cell plating); b) HCT116 WT and PTTG1−/− cells expressing an empty vector (WT+EV and PTTG1−/− +EV), and PTTG1 re-introduced PTTG1−/− (PTTG1−/− +PTTG1) cells were plated in 96-well plates for 24 hours and treated with control vehicle (C) or different doxorubicin doses for another 48 hours. DNA synthesis was assessed by measuring BrdU incorporation; c) HCT116 WT and PTTG1−/− cells were plated for 24 hours and treated with control vehicle (C) or doxorubicin (0.02 uM) for another 48 hours, fixed, stained for β-gal activity and cells counted; d) HCT116 WT and PTTG1−/− cells were plated for 24 hours and treated with control vehicle (C) or different doses of doxorubicin for another 48 hours, Tunel assay performed and positive cells counted. Each experiment was repeated three times. Results expressed as mean±SD, n = 3, *p<0.05, **p<0.001.